Construction Debris and Municipal Landfill Characteristics

[jjesik]

I'm working on a slope stability evaluation for two different landfills. One is primarily construction debris, such as 2x4's, concrete, rebar, glass, asphalt, etc... The other is primarily municiple waste.

I'm trying to figure out what some good numbers are for unti weight, c, and the friction angle. I've read some numbers in a couple of different books ranging from 20 to 84 pcf, c ranging from 0 to 40 (primarily for coal and fly ash debris though) and the friction angle ranging from 0 to 43 degrees.

These two landfills are valley/canyon fill landfills that are relatively old with no liners and more than likel'y will only have a soil cap with erosion controls, such as berms. The slopes range from about 3H:1V to 1H:1V. Slope heights are 50-70 feet.

They are in an arid region with no groundwater. The landfills are sitting on alluvium material (2 - 20 feet thick), mostly SC and a silty/clayey shale below the alluvium.

If anyone has any thoughts / experience of characterizing the material let me know. The material is covered and burried with a silty/lean clay material.

Grain size, moisture all the basic stuff has been done on the waste, but I don't have a clue of how to figure out an angle.

I was thinking of just using a conservative unit weight of 120pcf for the waste unless someone has a better idea.

Thanks,
AJ

 

[jdonville]

jjesik,

Landfills can be tricky - the old ones were constructed before modern standards and might contain almost anything, depending on the owner and the times. I worked on a landfill remediation project in Chicago where we actually had hydrogen gas being generated in the belly of the beast - but that is an extreme example.

1H:1V slopes also raise a big red flag for me. I hope that there are no significant fluid levels inside that slope.

Practically speaking, I wouldn't assume any cohesion, as I wouldn't think that the material would be homogeneous enough to characterize it that way. This also makes back calculating a minimum unit friction angle vs. average unit weight a little easier.

Unit weight is a little knottier. You should probably contact a landfill design firm to see what values they use for design.

Jeff


Jeffrey T. Donville, PE
TTL Associates, Inc.

http://www.ttlassoc.com

 

[eric1037]

Dr. James Hanson at Lawrence Technological University in Southfield, Michigan,

http://www.ltu.edu

has done a decent amount of research on engineering properties of landfill material. I think they even constructed a shear box to estimate strength,

 

[jjesik]

Thanks for the help Eric1037 and Jeff, I'll see if I can get a hold of Dr. Hansen or at least some of his work and go from there.

AJ